Add i18n for TaskCleanCollectionsAndPlaylists (#11248)

Co-authored-by: Niels van Velzen <nielsvanvelzen@users.noreply.github.com>

Emby.Server.Implementations/Localization/Core/en-US.json

@@ -125,5 +125,7 @@
     "TaskOptimizeDatabase": "Optimize database",
     "TaskOptimizeDatabaseDescription": "Compacts database and truncates free space. Running this task after scanning the library or doing other changes that imply database modifications might improve performance.",
     "TaskKeyframeExtractor": "Keyframe Extractor",
-    "TaskKeyframeExtractorDescription": "Extracts keyframes from video files to create more precise HLS playlists. This task may run for a long time."
+    "TaskKeyframeExtractorDescription": "Extracts keyframes from video files to create more precise HLS playlists. This task may run for a long time.",
+    "TaskCleanCollectionsAndPlaylists": "Clean up collections and playlists",
+    "TaskCleanCollectionsAndPlaylistsDescription": "Removes items from collections and playlists that no longer exist."
 }